package org.apache.solr.core;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * Used to request notification when the core is closed.
 * <p/>
 * Call
 * {@link org.apache.solr.core.SolrCore#addCloseHook(org.apache.solr.core.CloseHook)}
 * during the {@link org.apache.solr.util.plugin.SolrCoreAware#inform(SolrCore)}
 * method to add a close hook to your object.
 * <p/>
 * The close hook can be useful for releasing objects related to the request
 * handler (for instance, if you have a JDBC DataSource or something like that)
 */

public abstract class CloseHook {

	/**
	 * Method called when the given SolrCore object is closing / shutting down
	 * but before the update handler and searcher(s) are actually closed <br />
	 * <b>Important:</b> Keep the method implementation as short as possible. If
	 * it were to use any heavy i/o , network connections - it might be a better
	 * idea to launch in a separate Thread so as to not to block the process of
	 * shutting down a given SolrCore instance.
	 * 
	 * @param core
	 *            SolrCore object that is shutting down / closing
	 */
	public abstract void preClose(SolrCore core);

	/**
	 * Method called when the given SolrCore object has been shut down and
	 * update handlers and searchers are closed <br/>
	 * Use this method for post-close clean up operations e.g. deleting the
	 * index from disk. <br/>
	 * <b>The core's passed to the method is already closed and therefore, it's
	 * update handler or searcher should *NOT* be used</b>
	 * 
	 * <b>Important:</b> Keep the method implementation as short as possible. If
	 * it were to use any heavy i/o , network connections - it might be a better
	 * idea to launch in a separate Thread so as to not to block the process of
	 * shutting down a given SolrCore instance.
	 * 
	 * @param core
	 */
	public abstract void postClose(SolrCore core);
}
